1. Field of the Invention
The present invention relates to a light emitting diode (LED) chip package, and more particularly, to an LED chip package with improving entire light emitting efficiency by transmitting an excited light from an LED chip and absorbing the excited light in a phosphor and emitting a wavelength conversion light obtained by converting a wavelength of the excited light.
2. Description of the Related Art
A light emitting diode (LED) is a solid light emitting device formed of a semiconductor, which is more stable and reliable than other thermal conversion LEDs and has a long life. Also, since it is possible to drive the LED by using a voltage of several V and a current of several tens mA, power consumption is small, which makes utility thereof be increased. Such LED emits light close to approximately single color light, which is different from light having a wide light emitting spectrum from an incandescent bulb.
Recently, LEDs capable of emitting white light or embodying a plurality of colors have been developed. As a method of manufacturing a white light LED, there are a method of mixing LED chips of red, green, and blue to emit white light and a method of mixing an LED chip emitting light of a certain color with a phosphor emitting fluorescent light. White LEDs currently used are generally manufactured by using the latter method.
For example, a white LED chip package may be obtained by encapsulating a blue LED chip with a molding resin where yellow phosphors are scattered. When light in a wavelength of 460 nm is emitted from the blue LED chip, light in a wavelength of 545 nm is emitted from the yellow phosphor absorbing the light from the blue LED chip, thereby outputting white light by mixing two types of light whose wavelength is different from each other.
FIGS. 1A to 1D are cross-sectional views illustrating conventional LED chip packages emitting white light and various color light using phosphors as described above.
Referring to FIG. 1A, an LED chip package includes a package body 10, an LED chip 12 mounted on the package body 10, phosphors 14 scattered on the LED chip 12, and a transparent resin layer 16 containing the phosphors 14 and encapsulating the LED chip 12. In addition, not shown in the drawing, a lead frame and wire bonding may be further included to electrically connect the LED chip 12 to an external power supply thereof.
Since the phosphors 14 are concentrated on the LED chip 12, the LED chip package obtains an excited light from the LED chip 12 and a wavelength conversion light having a different wavelength from the excited light and emitted from the phosphors 14 absorbing the excited light easily returns to the LED chip 12 to be absorbed thereto, thereby increasing a temperature of the LED chip 12 in such a way that the LED chip 12 is deteriorated and becomes unreliable. Also, since a path where the excited light and the wavelength conversion light are transmitted to the outside of the LED chip package is long, which makes emission thereof disadvantageous. Also, due to heat generated when the LED chip 12 emits light, the phosphors 14 are deteriorated, which may have a bad effect on emitting light.
FIG. 1B illustrates an LED chip package where phosphors 24 are uniformly scattered in a transparent resin layer 26. Since a path where a wavelength conversion light is transmitted is relatively short in a structure of the LED chip package, emission thereof is easy. However, the excited light may be reflected before the phosphors 24 absorb excited light to return to an LED chip 22 to be exhausted or to be transmitted to a reflective plate to be exhausted via several reflections.
FIG. 1C illustrates an LED chip package including a remote phosphor layer 35, considering the defects as described above. In this case, phosphors 34 are not contained in a transparent resin layer 36 and form a layer in addition to the transparent resin layer 36. Accordingly, when an excited light is transmitted from an LED chip 32 to the phosphors 34, generates a wavelength conversion light, and is reflected by the phosphors to the inside a package body 30, the excited light may be hardly affected by the LED chip 32, pass through the package body 30, and be emitted outside. Also when being emitted to the inside of the package body 30, the wavelength conversion light may be continuously transmitted and emitted outside.
However, in this case, when the excited light and the wavelength conversion light are transmitted the inside of the package body 30, the excited light and the wavelength conversion light may be continuously reflected and transmitted to be exhausted or absorbed into the LED chip 32 to be exhausted. Accordingly, there is an attempt to increase an amount of light emitted outside of the package body 30 by diffuse reflecting light transmitted to the inside of the package body 30.
FIG. 1D illustrates an LED chip package including an LED chip 42, phosphors 44, a transparent resin layer 46, and a remote phosphor layer 45, the LED chip package being capable of diffuse reflecting and emitting an excited light and a wavelength conversion light transmitted inside by using diffuse reflection layers 41 and 41′ formed on a package body 40. By forming the diffuse reflection layers 41 and 41′, a light emitting device having higher light emitting efficiency may be manufactured.
Light emitting efficiencies of the LED chip packages shown in FIGS. 1A to 1D are approximately 45.3%, 66.6%, 61.7%, and 79.6%, which are gradually increased. However, there is still required higher light emitting efficiency.
FIG. 2 is a diagram illustrating a generation of a wavelength conversion light from an excited light in a conventional LED chip package. Referring to FIG. 2, there is shown an LED chip package where a remote phosphor layer is formed as FIGS. 1C and 1D.
Phosphors 54 are distributed a phosphor resin 55 capable of being mixed with phosphors and being formed on a package body. When an excited light L1 with a wavelength of λL1 enters into the phosphor 54, a wavelength conversion light L2 with a wavelength of λL2 different from that of the excited light is generated in the phosphors 54 and diffused in all directions. In this case, when the wavelength conversion light L2 is transmitted to a transparent resin layer 56, the wavelength conversion light L2 may be lost. That is, the wavelength conversion light L2 entering into a package body of the LED chip package may be exhausted while continuously reflected or may be exhausted while entering and being absorbed into an LED chip. Accordingly, due to a loss of the wavelength conversion light L2, entire light emitting efficiency of the LED chip package is reduced.